There is said that a three-dimensional vision is tired compared with an observation of usual 2D image, since an observation state different from daily life is produced. FIGS. 16(a) and (b) are diagrams explaining the observation principle of three-dimensional image, FIG. 16(a) shows right and left screen observed as a three-dimensional image, and FIG. 16(b) shows an observation state respectively.
In FIG. 16(b), numerals 21 and 22 designate a left eye and a right eye of a viewer, respectively, numeral 23 designates a display screen where the screen for right eye and the screen for left eye are overlapped and displayed, numeral 24 designates figure A on the right screen shown in FIG. 16(a), and numeral 25 designates figure A on the left screen shown in FIG. 16(a).
As shown in FIG. 16(b), places in right and left figures A are shifted, so that in the case of paying attention to this, sight lines of viewer are intersected on this side of the screen, and thus the stereo image in figure A seems to dash out from the screen forward. Here, the angle that the sight lines crowd, is referred to as a vergence angle, and a right and left positional deviation is referred to as a parallax. On the one hand, the focus adjustment of eyes is suitable on the screen, so that the adjusting distance of the focus adjustment and the vergence distance to the point that the lines of sight from eyes intersect, are different.
Such an observation state is not generated in the daily life, so that the indistinctness and the unnaturalness might be felt. In the contents that contain a lot of rapid parallax changes to which the parallax is large, and subject dashes out from the screen particularly, it becomes harder to see while a strong stereo effect is obtained, so that it is necessary to avoid audience for a long time.
In consideration of this respect, for example, in Japanese Patent Application Opened No. 355,808/1999, there is proposed an image system that the parallax amount of the three-dimensional image signal is detected, and the operation that the degree of influence given to the viewer is assumed based on the parallax amount, and the display is switched to usual 2D image or the like, is controlled thereby avoiding the long time audience of the image with a large degree of influence to emphasize the stereo effect. Moreover, in the above patent specification, there is proposed an image system that the parallax amount is controlled so as to decrease the adjustment of eyes and the shift of the convergence, thereby avoiding the long time audience of the image with a large degree of influence.
However, in the above patent specification, a concrete method of evaluating a rapid change in parallax is not shown. Moreover, concrete measures against the error at the measuring and the noise of the image are not shown, so that it is likely not to function well according to the image.